Pests and Diseases

Koa wilt is a serious, often fatal disease of the native Hawaiian koa, Acacia koa. Trees affected with the disease rapidly lose their canopies and may die within a few months.

Koa moth (Scotorythra paludicola)

A sudden outbreak of the koa looper moth has occurred in the Hilo and Hamakua districts of Hawaii Island since January 2013. The moth has defoliated koa trees (Acacia koa) over tens of thousands of acres of windward, lower elevation forests. Outbreaks of this native insect have occurred regularly on Maui but have not been observed on Hawaii Island for 50 years. Koa trees in good health will probably survive defoliation but with reduced growth. For more information see the Hawaii DLNR Division of Forestry and Wildlife’s koa moth fact sheet. More photos of the moth, caterpillars, damage to leaves, and defoliated koa stands may be found at the koa moth gallery,Will Haines' (UH CTAHR) gallery, and at Karl Magnacca’s (DLNR – DOFAW) on-line gallery.

A new rust pathogen has been discovered infecting ohia, eucalyptus, rose apple, and other trees in the Myrtaceae. This fungus could be a serious pest both in native forests and on tree farms and in nurseries.

Myoporum thrips

A new species of thrips (Klambothrips myopori) has recently been discovered attacking naio (Myoporum sandwicense) on Hawaii Island. These insects have been injuring and killing other species of Myoporum in California and have now arrived in Hawaii. The insects cause gall-like damage in young leaves and may eventually kill the tree. They initially were found on cultivated naio papa at resort areas in the South Kohala and North Kona districts and Waikoloa Village and have spread to natural naio populations in Kau and Hawaii Volcanoes National Park and has been found on landscape plantings in Hilo. These thrips only attack naio (Myoporum spp.) To prevent this pest from spreading to neighbor islands, please do not move naio off Hawaii Island. If you find these insects attacking naio on other islands, especially wild populations, please notify Cynthia King, Hawaii Division of Forestry and Wildlife Entomologist, (808) 587-0019, or by email at cynthia.b.king@hawaii.gov, or call the Hawaii Pest Hotline 643-PEST.